Aspects of this disclosure are generally related to data storage systems. Data storage systems are used to maintain relatively large data sets and support a relatively large number of concurrent users. The basic building blocks of a data storage system may include storage arrays or clustered storage servers. Examples of storage arrays include but are not limited to the Symmetrix and VMAX families of products of EMC Corporation. Each storage array or storage server may include multiple data storage devices, processors and cache resources. The data storage system presents logical storage devices to applications running on host devices and responds to IOs which reference the logical storage devices by using a mapping between the logical storage devices and physical storage devices on which data is stored. A variety of features may be implemented to avoid data loss and maintain data availability.